I've read the similar question on wireless connections dropping, but no answer seems to apply to my case

I have configured the wi-fi lan of my router to broadcast sid and use WPA-PSK. Every few minutes my wi-fi connection drops for a few seconds and then restores.

When I use two computers and run a ping -n 50000 on both computers, I see that the connection drops at different times but with almost the same rate.

the router is a zyxel, one pc runs windws vista and uses a USB wi-fi device from Belkin: F6D4050 the other one runs windows 7 is a Dell PC with an Intel(R) WiFi Link 5100 AGN

there are no other wi-fi lans around